Critical voltage for Fanuc 21i maint battery?

We have an older machine that is currently not under power. We were going to move it and hook it back up for use but realized the main batt is getting low. I cannot find any spec on when the memory will actually be lost? The battery pack is a 4xDcell pack on the cabinet so 6V. I am reading it at 5.13V currently. I know there is a little wiggle in there but curious if anyone might know where that is? Not sure if we need to start scrambling to chase parameters or not......

I'd be concerned also. Your at about 85% of rated voltage. The only spec I recall is plus/ minus 10% but that was to do with mains incoming voltage. I doubt you have lost parameters yet, but I'd action that.

The joy of those 4 - D size battery holders, they normally have screw terminals on them. You can piggy back 6V DC onto them while you change the batteries.

Regards Phil.

We plan to get power to the machine in the next couple weeks. I know we could probably jumper something in there but there is always some risk and if the system is already lost, that is a waste, or we could screw up.

It really is sort of a "good question" as I know all systems that use a battery have some sort of regulator that is lower voltage. Like Cmos, which is likely what this is could run as low as 3.3V.

Another Fanuc we have uses 3 D cells for 4.5V on the CNC and another 4x for 6V on the encoders. So seeing the 6V on the CNC side I was hopeful that they added more voltage for more headroom.

huleo said:

We plan to get power to the machine in the next couple weeks. I know we could probably jumper something in there but there is always some risk and if the system is already lost, that is a waste, or we could screw up.

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So your not prepared to do anything? What was the purpose of this thread,

Can you read any of the chip numbers on the board? If you can and there not custom the data sheet should give you the answer. Thoes batteries are well into approaching the rapid part of there discharge curve, add in falling temperatures at this time of year and i would expect there voltage to drop significantly more in the next 2 weeks than they have in the previous month or 2. Falling temps and battery age - state of discharge will make for a very non linear decay rate.

Weather that puts you in danger i don't know, i just know its decaying. Just because theres a regulator does not help you here either, it positively harms you, for the simple fact you have to give most regulators more voltage than they put out, at this point the regulator is rapidly not becoming your friend! That said it is your friend if you temp hook something up and swap the batteries for new ones as any sudden higher spike won't cause harm.

Machine has sat for 2yrs. I doubt 2 weeks will change much. The alkaline discharge curve indicates batteries are certainly not on the ragged edge of plummet as then fall quickly from 1.5V to 1.3V, then have a linear decline for some time.

Reponding to Mach, the purpose of the thread was to see if anyone had determined if there is a critical voltage threshold in which memory is actually lost?

Ok its linear but you need to consider temp, if the machines not in heated space, or if its going to get moved through colder spaces long enough to lose temp. This could well push you bellow 5v, which is a common PC - digital electronics voltage level. next common one bellow that is 3.3v logic, but i doubt memory would be at either of thoes, but the supply to the memory probably needs to be at around one of those 2 common voltages unless fanucs gone really weird? That would be more my concern than at this point of 2 years duration weather another couple of weeks going to be critical or not.

The 4xD cell is probably only for the absolute encoders.

The 21i standard configuration uses a separate lithium battery to maintain the CNC data. Optionally there was a 2xD cell holder that the builder could spec to replace the lithium cell.

Vancbiker said:

The 4xD cell is probably only for the absolute encoders .

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I would agree with that.

Pretty sure there is a Li battery behind the screen for parameters.

AFAIK, all Fanuc control from the 16A/18A onward used a small lithium battery in the power supply, accessible from the front.